1. PHYS208 - spring 2010 - page 1 PHYS208 Lecture Wednesday 14 th April 2010 Semiconductors Impurities - doping

2. PHYS208 - spring 2010 - page 2 We have gone through We have gone through: http://web.ift.uib.no/AMOS/PHYS208/2008/2008_04_09_Semiconductor-impurity.pdf We have also used parts of (exam presentation) http://web.ift.uib.no/AMOS/PHYS208/TEXT2010/Exam_2008_LATEX/pn_junction_Ex_2008.pdf We started to discuss thursday's and following week's text (handwritten notes) http://web.ift.uib.no/AMOS/PHYS208/2008/2008_P-N-junction.pdf ( to be used together with the above pn_junction_Ex_2008.pdf Some of the formalism is nicely discussed also in (mainly coming lectures material) http://web.ift.uib.no/AMOS/PHYS208/TEXT2008/phys208_Trygve_SLIDES.pdf

3. PHYS208 - spring 2010 - page 3 Density of states in band Fermi distribution Product of Density of states and Fermi distribution

4. PHYS208 - spring 2010 - page 4 Electrons and holes When we reverse energy, the holes take the same role as electrons  note the – sign on  2008 SLIDE NOTE

5. PHYS208 - spring 2010 - page 5 The task here was to arrive at the semiconductor equation, which leads to obtaining a product of n electrons times n holes as a function of temperature Taking a product,  gets eliminated

6. PHYS208 - spring 2010 - page 6 Once more about electrons and holes; Ferromagnetic fluid story once more Concept of holes

7. PHYS208 - spring 2010 - page 7 semiconductor equation, which leads to obtaining a product of n electrons times n holes - function of temperature. Taking a product,  eliminated Last time revisiting this (  evaluation is in the exam slides )

8. PHYS208 - spring 2010 - page 8 Starting Impurities Semiconductors might contain various impurities. However, only the type of impurities discussed below – DOPING by controlled impurities of one or other type P or N and the abrupt JUNCTION ( two types of doping in the same crystal structure with a sharp border ) appears to be useful for devices and instruments

9. PHYS208 - spring 2010 - page 9 Impurity atoms have 3 valence electrons Acceptor P-type (hole, positive charge carriers) Impurity atoms have 5 valence electrons Donor N-type (electron, negative charge carriers) PN

10. PHYS208 - spring 2010 - page 10 The atom-like states of impurities explained; Bohr-like 'atom' relations More details on the followin slide from 2008....

11. PHYS208 - spring 2010 - page 11 Impurity States – Donors from 2008 slide

12. PHYS208 - spring 2010 - page 12 Starting P-N junction

13. PHYS208 - spring 2010 - page 13 For work with P-N junction Exam presentation http://web.ift.uib.no/AMOS/PHYS208/TEXT2010/Exam_2008_LATEX/pn_junction_Ex_2008.pdf thursday's and following week's text (handwritten notes) http://web.ift.uib.no/AMOS/PHYS208/2008/2008_P-N-junction.pdf ( to be used together with the above pn_junction_Ex_2008.pdf ) Some of the formalism is nicely discussed also in http://web.ift.uib.no/AMOS/PHYS208/TEXT2008/phys208_Trygve_SLIDES.pdf